The skin is the greatest and most visible organ of the body of animals including human, and mainly consists of the epithelium and the dermis, and has several accessory structures such as sweat glands, sebaceous glands and hair follicles.
In addition, the skin is an organ that is most frequently exposed to environmental stresses, hazards and pathogens among the tissues of the body. Therefore, the skin has many functions, for example, a protection-barrier functions to external invasions (for example, heat, chemical agents and bacteria), a heat-regulation function, a dehydration-prevention function, and further a sensory function. Accordingly, maintenance and establishment of the skin health is important for the health of the animal.
As one of the methods of evaluating the skin condition or evaluating ingredients improving the skin condition, a method is known so far in which the aging state or inflammation state of the skin is evaluated by measuring the gene expression level (Patent Documents 1 and 2). Particularly with respect to the wrinkle and the aging state, known is a method of evaluating certain proteins and expression of genes and the like on the skin irradiated with ultraviolet ray, and, (Patent Documents 3 and 4).